Method of making stereotype materices and backing sheet for use therein



Dec. 28, 1965 c, sc 3,225,687

METHOD OF MAKING STEREOTYPE RIGES AND BACKING SHEET FOR USE REIN 2 Sheets-Sheet 1 Filed June 10, 1965 IN ENTOR. MM

BY BRUCE M. COLL/NS United States Patent 3,225 687 METHOD OF MAKENG STEREOTYPE MATRICES AND BACKING SHEET FOR USE THEREHN Charles Fritschi, 5427 Wynnefieid Ave, Philadelphia, Pa. Filed June 10, 1963, Ser. No. 286,603 8 Claims. (El. 10117) This invention relates to backing sheets for stereotype matrices, to methods for producing such matrices by use of these backing sheets, and to matrices thereby made.

The main objects of the present invention are to provide an improved stereotype matrix, a method of automatically and permanently combining a backing sheet with the main body of the matrix by the usual molding, drying and forming operations, in such a way so as to produce a substantially uniform planar bearing for the back side of the matrix and adequate support for casting is provided for the non-image or space areas of the matrix; and backing sheets which are suitable for the above methods and objectives. Other objects and advantages will be apparent hereafter.

The flong or stereotype mat of the type which is in common use and to which the present invention relates consists of a relatively thick sheet of felted cellulose fibers, such as rag stock, cotton linters, chemical Wood pulp, such as suiphite or soda pulp, alpha, and the like. It usually contains fillers, such as powdered clay, talc, etc., mixed with the fibers in the body of the mat.

Newspaper mats are usually shipped in humidified condition, ready for use. Under pressure of approximately 3000 p.s.i., applied either by a matrix roller or a so-called direct pressure press, in conjunction with one or more intermediate resilient blankets, the plasticity of the moistened flong or mat enables it to take a welldefined impression of the form or pattern comprising body type, display type, rules, cuts, etc., with open or space areas therebetween, the composite whereof is herein referred to as the surface characteristics of the type form.

After stripping the mat from the form, it is dried, packed, trimmed to accurate dimensions and formed to a semi-circular or tubular shape. One or more plates of stereotype metal are then cast from the matrix and after shaving and trimming, the plates are employed on a rotary printing press.

However, this conventional type of matrix and method of producing the same have certain disadvantages, the chief among which is the necessity to manually pack the larger open (non-image) areas thereof with small strips of gummed felt. This packing operation requires considerable skill, care and time since these felt strips must be individually selected and spaced to suit the varying size and depth of the open areas. If underpacked, open spaces tend to cave in during the subsequent casting operation due to the pressure of the liquid metal against the face of the mat and the vacuum usually applied at the back side of the mat. The resulting loss of space depth in the corresponding plate areas requires hand tooling to prevent smudges on the printed page. On the other hand, if the mat is overpacked, concavity of large type and solids and other distortions of the printing level are apt to occur.

It is well known that hand packing of mats is a bottleneck in printing, particularly in newspaper production. A number of attempts have been made to eliminate the cumbersome and costly method of manual packing but due to unreliability, lack of speed and excessive cost, none of these attempts have gained acceptance in the industry. One exception is the so-called one-piece packless mats which have considerably reduced the need of 'ice hand packing. However, these packless mats have a number of disadvantages, among which are high first cost, slow drying and forming, and need of mechanical changes and adjustments in the existing equipment.

The present invention, which overcomes these and other problems in the prior art of matrix making, is explained in the following description when read in conjunction with the drawings, in which:

FIGURE 1 is an enlarged plan view of one side of a small portion of the backing sheet provided by this invention, the circles in solid lines indicating the protuberances on the upper or coated surface, and the circles in dotted lines indicating the protuberances on the lower or uncoated surface, and the indentations being denoted by the spaces between the circles.

FIGURE 2 is a cross-section taken along lines 2-2 of FIGURE 1.

FIGURE 3 is a cross-section taken along lines 3-3 of of FIGURE 1.

FIGURE 4 is a cross-section corresponding to FIGURE 3 showing a typical adhesive coating pattern.

FIGURE 5 is an enlarged plan view similar to FIG- URE 1 of one side of a small portion of a backing sheet having protuberances of an alternative configuration.

FIGURE 6 is a cross-section taken along lines 66 of FIGURE 5.

FIGURE 7 is an enlarged transverse sectional view of the elements comprised in the molding operation before application of pressure.

FIGURE 8 is an enlarged transverse view of the matrix as it appears after molding but before the drying-andforming operation.

FIGURE 9 is a similarly enlarged sectional view of the matrix after the usual drying-and-forming operation.

FIGURE 10 is an enlarged sectional view of a stereotype plate cast from the matrix as shown in FIGURE 9 and taken transverse to the curve of the plate.

More particularly FIGURES l to 4 demonstrates the conformation of the closely spaced protuberances 11 of the backing sheet of the present invention. These protuberances need not be semi-spherical, as shown in FIG- URES 1 to 4, but may be of a polyhedral shape of which 12 shown in FIGURES 5 and 6 is but one example.

By reason of the nature of the present invention, the material of which the novel backing sheet is composed must be stretchable both in the machine direction and in the cross-machine direction. The preferred type of material is a kraft paper cross-creped from a caliper of about .005 inch to a caliper of about .025 inch, preferably from about .006 inch to about .018 inch, and then indented to an overall thickness of about .06 inch.

Due to the nature of the material, the protuberances are crushable under pressure. The protuberances are indented so as to be of substantially equal height and equal size. By regularly spacing these protuberances on both sides of the backing sheet, the convexities of the protuberances on one side define concavities between the protuberances on the other side.

The indenting of the dry web of crepe paper is performed in the usual way with a pair of matched embossing rolls designed to emboss the closely spaced protuberances 11 into the paper.

One side of the backing sheet herein described is then coated, as for example, by roller-and-brush, air-knife, or like methods, with an aqueously activated adhesive 13, such as fish glue, dextrine, polyvinyl alcohol, polyvinyl acetate, and the like, as well as combinations thereof. The adhesive coverage may vary from about 50% up to 100% of the total available surface area, preferably at least and ideally from about to When the entire surface area is coated, however, a vapor barrier may be created during the drying operation, thus creating the possibility of incomplete drying and delamination. This difficulty may be overcome by either slower drying or by coating the backing sheet before the embossing operation, in such a way that fractures are created in the coating at the tips of the protuberances which permit free passage of the vapor. It has been found ger1- erally preferable however to selectively coat the backing sheet after the embossing operation and to cover less than the total area. The resulting uncoated areas thus permit escape of the water vapor released during the drying operation.

In determining the percentage of adhesive coverage, it must be remembered that insufiicient coverage will result in bond failure and in excessive absorption of moisture by the protuberances, thereby weakening their support capability, since the adhesive coating also serves to add strength to the protuberances during the molding, drying, and casting operations.

Due to the nature of the backing sheet 14, as shown in FIGURE 7, it has the ability to shrink during the usual drying-and-forrning operation in exact conformity with the humidified flong 15. This advantage is realized without an increase in the time period normally required for drying and forming a hand-packed mat of the same characteristics and moisture content, and without need of previous moistening or conditioning the backing sheet. This latter feature greatly simplifies the use, storage, packaging and shippin of the backing sheets, and provides indefinite shelf life.

In the actual application of this invention, the coated side of humidified flong is placed next to the type form 16 as shown in FIGURE 7. The surface characteristics of the type form within chase 17 may include small type 18, large type 19, .853 inch base for halftone cut 20, .895 inch base for open space 21, .853 inch base for open space 22, and the like. The adhesive-coated side of the dry backing sheet 14 is then placed next to the rear face or surface of fiong 15, and one or more molding blankets 23 are positioned against the rear surface of the backing sheet, followed by two or three molding boards 24 and 25.

The molding blanket or blankets may consist of rubber impregnated fabric, felt, cork, or the like, as well as a combination of such materials, generally having a total thickness of from about .055 inch to about .08 inch, but preferably a thickness of about .065 inch. While more than one blanket may be used, excellent results can be realized with the use of only one.

The molding boards are the type of common usage, one preferably having a thickness of about .125 inch and one preferably having a thickness of about .062 inch. The individual thickness may vary but the total thickness of the boards should generally not exceed .187 inch.

When employing a roller-type press, a minimum of two such boards should be used. When employing a so-called direct pressure press, only one such board is required.

The molding operation then converts the flong into a matrix or female replica as shown in FIGURE 8 of the surface characteristics of the type form shown in FIG- URE 7 down to the shoulder of the type. At the same time, it completely flattens the protuberances 11 of the backing sheet in the image or printing areas 26, 27, 28 and 29 and compresses them to a thickness slightly exceeding the depth of the space or non-printing areas 30 and 31 of the mat.

Under the molding pressure, a sufiicient quantity of moisture is squeezed out of the matrix to reactivate the adhesive coating of the backing sheet. While this reactivation is much less effective in the space areas than in the image areas of the mat, due to the lesser pressure applied in the former, it nevertheless produces a sutficient temporary bond between mat and backing sheet across substantially the entire surface.

The trimming of the mat and the usual dryingandforming operation should follow the molding operation as 4 quickly as possible to perfect the bond between matrix and backing sheet and to produce at the same time, by vacuum or centrifugal action, a uniform level for the entire back of the mat, and effective support for its open spaces, as shown in FIGURE 9, by selectively further compressing the protuberances in the open spaces and by slightly increasing in the mat any space depth which is too shallow in the type form.

The resulting automatically packed mat has the backing sheet now securely adhered to it, as shown in FIG- URE 9. It demonstrates a unitary nature and is ready for the casting operation which produces a stereotype printing plate, as shown in FIGURE 10, in which the surface characteristics of the type form shown in FIGURE 7 are faithfully reproduced, including open space 21 having the right depth and dimension to permit adhesively mounting of plastic engraving 32 for direct printing, without need of the customary application of a special spacing element on the back of the mat.

The nature of backing sheet 14 permits use of a molding blanket of a thickness of about .065 inch instead of the customary thickness of about .25 inch necessary when using conventional hand-packed mats. This substantial reduction in blanket thickness produces a demonstrably greater accuracy in the thickness of the mechanically packed mat at the printing levels, of halftones, solids, display type, body type, rules, and the like. Consequently, the printing quality of press plates cast from such mats is improved.

It is to be appreciated that the precise linear dimensions given in the foregoing specification are based upon the equipment currently employed in the newspaper industry. Quite obviously the present invention is not limited to these dimensions. Different equipment or printing techniques may similarly utilize this invention with appropriate changes in specific dimensions.

Accordingly, by use of the backing sheet and methods herein described, there is produced an improved matrix requiring no manual packing. It also is to be understood that the details of this process and product and the particular embodiments of the invention herein described and shown may be altered without departing from the spirit of the invention as defined by the following claims.

What is claimed is:

1. A stereotype matrix backing sheet consisting of (a) a single sheet of paper cross-creped to a thickness of about three to about five times its original thickness and indented on both facial surfaces with a plurality of crushable protuberances of substantially equal dimensions, the protuberances being uniformly spaced so that the convexities of the protuberances on either facial surface define the concavities between the protuberances on the other facial surface, the overal thickness of the backing sheet after indentation, measured from the tips of the protuberances on one facial surface to the tips of the protuberances on the other facial surface, being from about ten to about twelve times the original thickness of the paper before cross-creping, and

(b) an aqueously activated adhesive in a substantially tackless condition affixed to the uppermost portion of the protuberances on one facial surface and covering at least 50% of that surface.

2. A stereotype matrix backing sheet according to claim 1 wherein the adhesive covers at least of the area of the side of the backing sheet so covered.

3. A stereotype matrix backing sheet according to claim 1 wherein the protuberances are substantially semi-spherical in shape.

4. A stereotype matrix backing sheet according to claim 1 wherein the aqueously activated adhesive comprises a member selected from the group consisting of fish glue, dextrines, polyvinyl alcohol and polyvinyl acetate.

5. A stereotype matrix backing sheet according to claim 1 wherein the backing sheet is cross-creped kraft paper.

6. In the method of making a stereotype matrix in which a mat is formed by pressing a moist flong between a type form and a molding blanket, said type form having surface characteristics of image and non-image areas, whereby the 'fiong is impressed with the surface characteristics of the type form, the steps which comprise (1) placing between the flong and the molding blanket .a back-sheet consisting of (a) a single sheet of paper cross-creped to a thickness of about three to about five times its original thickness and indented on both facial surfaces with a plurality of crushable protuberances of substantially equal dimensions, the protuberances being uniformly spaced so that the convexities of the protuberances on either facial surface define the concavities between the protuberances on the other facial surface, the overall thickness of the backing sheet after indentation, measured from the tips of the protuberances on one facial surface to the tips of the protuberances on the other facial surface, being from about ten to about twelve times the original thickness of the paper before cross-creping, and

(b) an aqueously activated adhesive in a substantially tackless condition affixed to the uppermost portion of the protuberances on one facial surface and covering at least 50% of that surface so that the uppermost portions of the protuberances on the facial surface of the backing sheet having the adhesive thereto afiixed are in substantial contact with the flong,

(2) applying suflicient pressure to impress the flong with the surface characteristics of the type form so as to form a mat, the protuberances of the backing 6 sheet which are in image areas thereby being completely flattened while those which are in non-image areas are compressed to a thickness slightly exceeding the depth of the non-image areas, and the adhesive thereby being activated by the moisture squeezed out of the fiong, and

(3) drying and forming the combined mat and backing sheet so as to perfect the bond between the two and provide adequate support in the non-image areas for subsequent casting, the drying and forming being performed under a force differential between the face of the mat and the back of the backing sheet to further compress the protuberances in the non-image areas until a substantially uniform level is obtained on the 'back of the combined mat and backing sheet.

7. The method of claim 6 wherein the force differential is supplied by vacuum.

8. The method of claim 6 wherein the force of diflerential is supplied by centrifugal action.

References Cited by the Examiner UNITED STATES PATENTS DAVID KLEIN, Primary Examiner. 

6. IN THE METHOD OF MAKING A STEREOTYPE MATRIX IN WHICH A MAT IS FORMED BY PRESSING A MOIST FLONG BETWEEN A TYPE FORM AND A MOLDING BLANKET, SAID TYPE FORM HAVING SURFACE CHARACTERISTICS OF IMAGE AND NON-IMAGE AREAS, WHEREBY THE FLONG IS IMPRESSED WITH THE SURFACE CHARACTERISTICS OF THE TYPE FORM, THE STEPS WHICH COMPRISE (1) PLACING BETWEEN THE FLONG AND THE MOLDING BLANKET A BACK-SHEET CONSISTING OF (A) A SINGLE SHEET OF PAPER CROSS-CREPED TO A THICKNESS OF ABOUT THREE TO ABOUT FIVE TIMES ITS ORIGINAL THICKNESS AND INDENTED ON BOTH FACIAL SURFACES WITH A PLURALITY OF CRUSHABLE PROTUBERANCES OF SUBSTANTIALLY EQUAL DIMENSIONS, THE PROTUBERANCES BEING UNIFORMLY SPACED SO THAT THE CONVEXITIES OF THE PROTUBERANCES ON EITHER FACIL SURFACE DEFINE THE CONCAVITIES BETWEEN THE PROTUBERANCES ON THE OTHER FACIL SURFACE, THE OVERALL THICKNESS OF THE BACKING SHEET AFTER INDENTATION, MEASURED FROM THE TIPS OF THE PROTUBERANCES ON ONE FACIL SURFACE TO THE TIPS OF THE PROTUBERANCES ON THE OTHER FACIL SURFACE, BEING FROM ABOUT TEN TO ABOUT TWELVE TIMES THE ORIGINAL THICKNESS OF THE PAPER BEFORE CROSS-CREPING, AND (B) AN AQUEOUSLY ACTIVATED ADHESIVE IN A SUBSTANTIALLY TACKLES CONDITION AFFIXED TO THE UPPERMOST PORTION OF THE PROTUBERANCES ON ONE FACIL SURFACE AND COVERING AT LEAST 50% OF THAT SURFACE SO THAT THE UPPERMOST PORTIONS OF THE PROTUBERANCES ON THE FACIL SURFACE OF THE BACKING SHEET HAVING THE ADHESIVE THERETO AFFIXED ARE IN SUBSTANTIAL CONTACT WITH THE FLONG, (2) APPLYING SUFFICIENT PRESSURE TO IMPRESS THE FLONG WITH THE SURFACE CHARACTERISTICS OF THE TYPE FROM SO AS TO FORM A MAT, THE PROTUBERANCES OF THE BACKING SHEET WHICH ARE IN IMAGE AREAS THEREBY BEING COMPLETELY FLATTENED WHILE THOSE WHICH ARE IN NON-IMAGE AREAS ARE COMPRESSED TO A THICKNESS SLIGHTLY EXCEEDING THE DEPTH OF THE NON-IMAGE AREAS, AND THE ADHESIVE THEREBY BEING ACTIVATED BY THE MOISTURE SQUEEZED OUT OF THE FLONG, AND (3) DRYING AND FORMING THE COMBINED MAT AND BACKING SHEET SO AS TO PERFECT THE BOND BETWEEN THE TWO AND PROVIDE ADEQUATE SUPPORT IN THE NON-IMAGE AREAS FOR SUBSEQUENT CASTING, THE DYRING AND FORMING BEING PERFORMED UNDER A FORCE DIFFERENTIAL BETWEEN THE FACE OF THE MAT AND THE BACK OF THE BACKING SHEET TO FURTHER COMPRESS THE PROTUBERANCES IN THE NON-IMAGE AREAS UNTIL A SUBSTANTIALLY UNIFORM LEVEL IS OBTAINED ON THE BACK OF THE COMBINED MAT AND BACKING SHEET. 